Has a prime minister ever won an election with so little support as Tony Blair now enjoys? Even Margaret Thatcher, loathed in much of the country, retained millions of fervent admirers. Now, much of the country seems in an almost cathartic state, describing the political leader it is about to re-elect as a war criminal and a compulsive liar. Among those planning to vote Labour, there is nearly always a "despite", with much talk of gritted teeth and nose pegs. Labour will get many votes on the understanding that the premiership will soon pass to Gordon Brown, a man who in some minds now carries hopes that a Mandela or a JFK would struggle to satisfy. Perhaps this is Mr Blair's final revenge: a poisoned chalice of expectation.

Yet two considerations compel a Labour vote on 5 May. First, Michael Howard's campaign deserves to fail, and fail miserably. As he says, it is not racist to talk about asylum and immigration. But it is racist to turn "asylum-seeker" (which, lest we forget, is someone fleeing persecution) into a term of abuse, to conflate "illegals" with immigrants generally, and to make this the central platform of a party campaign, to the extent that most voters have no clear idea of any other Tory policy. "Are you thinking what we're thinking?" invited the response "Yes, let's send them home", the "them" being sufficiently vague to encompass almost anybody with a dark skin or a foreign accent. A few weeks ago, a small rise in Tory seats and votes may have seemed tolerable. Not so now.

Second, Labour's commitment to beating poverty and improving public services demands support. True, as the Institute for Fiscal Studies points out, it has not closed the gap between rich and poor - but nor has the gap widened during Labour's period in office, and that itself is some achievement, given the pressures of a globalised economy. As for health and education, these services were starved of investment for 18 years, to the point where they were near collapse. It will take at least 18 years to rebuild them, and a Tory restoration now would surely destroy them for good. Battles against, say, privatisation and 11-plus selection have to be fought, whichever party is in power. With Labour in office, they can be won.

Many, including a high proportion of NS readers (see cover story), will feel that a Liberal Democrat vote is an acceptable alternative, given Mr Blair's prosecution of a murderous, illegal war. The Lib Dems do not truly favour social justice though, oddly, some of their policies are now more solidaristic than Labour's. But those who argued that the Lib Dems were worthy recipients of anti-Tory tactical votes in the past cannot now say that they are unworthy of tactical votes designed to damage right-wing elements in Labour. Either the Lib Dems are decent progressives or they are not.

Some may say the most pro-war ministers and MPs deserve to lose their seats to the Lib Dems, if only pour encourager les autres. Perhaps. But there can be no argument for risking a single Tory gain - or even forgoing a Tory loss - to spite Mr Blair. General elections are about the next four years, not about the past four. Ask yourself what kind of people you want in the Commons when it debates wars, race, abortion, gays or Africa. Think what it would be like if nobody except powerless opposition MPs listened to or cared what you thought. Ask if you want to see Robin Cook or Glenda Jackson on the opposition benches. We owe it to millions of poor people here and abroad to ensure Labour - not Mr Blair, not even Mr Brown, but its MPs, its activists, its union supporters - remains the party in power. Then, at least, the voices of the deprived will be heard, however faintly, where it matters.